Magnesium base alloy



Patented Nov. 12, 1940 MAGNESIUM BASE ALLOY John C. McDonald, Midland,Mich., assignor to The Dow Chemical Company, Midland, Micht, acorporation of Michigan Ne Drawing. Application November 13, 1939,Serial No. 304,128

3 Claims. (01. 75-168) The invention relates to magnesium base alloys,and more particularly concerns alloys of this nature having improvedphysical properties, such as a high degree of formability associated bwith excellent tensile and yield strengths.

Magnesium alloys are finding increasing use in structural and mechanicalarts where a light weightmetal is highly desirable, such as for use inmaking large castings, forgings, and the like.

However, the use of these alloys in the rolled form to make sheet metalarticles requiring forming operations has not progressed as rapidly, dueto the fact that in general alloys of good formability permittingrelatively sharp bends to be made without the article developingexternal cracks usually have inferior characteristics as regards theiryield and tensile strengths.

the alloy contains from 3 to 6 per cent of silver, from 0.1 to 0.3 percent of calcium, and from 6 to 8 per cent of cadmium. Alloys containinghigher percentages of alloying ingredients, while still having goodductility, have exceptionally 5 high yield and tensile strengths, andthus are also very suitable for use in casting operations as well asforming operations.

The following table, which lists some of the properties of rolled sheetmetal made from my 10 new alloy and compares these properties with thoseof related parent alloys, illustrates the improvement in yield strength,tensile strength, and ductility as represented by the per cent increasein elongation of the new alloy over the corre- 5 sponding properties ofthe closely related ternary alloys.

Table Nominalcomposition in 20 percent (balanee Annealed 001d rolledmagnesium Yield Tensile Per cent Yield Tensile Per cent Ag Ca Cdstrength strength elongation strength strength elongation I inlbalsq.in. in lbs/sq. in in 2 inches in lbs/sq. in." in1bs./sq.in. in 2 inches25 0. 3 5. 1 10, 000 31, 000 15 31, 000 30, 000 2 0. s 4.3 10,000 31,00014 27,000 34,000 2 3'3 3'2 55% it 2 22m t 013 914 151000 321000 1732,000 331000 2 30 It is, accordingly, the principal object of theinvention to provide a magnesium base alloy which may be made into arolled sheet or the like, possessing a sufficient degree of ductility oriormability to be sharply bent, drawn, or otherwise shaped, while stillhaving excellent tensile and yield strengths. Other objects andadvantages will be apparen as the description of the invention proceeds.My invention resides inthe discovery that a magnesium base alloycomposed of from 0.5 to 10 per cent of silver, 0.05 to 1 per cent ofcalcium, and 1 to 15 per cent of cadium, the balance being substantiallyall magnesium, is endowed with the aforementioned properties. While theproperties of improved formability, associated with high tensile andyield strengths, are manifest over the entire range of compositionindicated,

I have found that in general a preferred com-- bination of properties,such as the most desirable ductility for forming operations togetherwith high tensile and yield strengths, is obtained when The propertieslisted in the above table under the section headed by the term annealedwere 35 obtained by first rolling the alloys at a temperature betweenabout 600 to 800 F., and thereafter annealing them at varioustemperatures through a temperature range of from 400 to 800 F. Theproperties selected for the table were those of 40 the annealedspecimens which exhibited the maximum elongation. The properties listedunder the, section headed cold rolled were obtained by subjectingspecimens of the alloys which had been hot rolled at a temperature offrom 600 to 45 800 F. to additional rolling in the cold state to bringabout a total reduction in thickness of from 2 to 10 per cent. Theproperties selected for the table were those of the cold rolledspecimens which showed the greatest tensile and yield 50 strengths,while having at least a 1 per cent elongation in 2 inches. 3

By comparison of the properties listed in the above table, it will beobserved that the'combined properties of my new quarternary alloy 55will be noted in the other portions of the amenable to solution andprecipitation heat treatments which, accordingly, modify its properties.

The new alloy may be compounded in any of the ways known in the art,such as by adding the alloying ingredients to the molten magnesium undera suitable flux. The flux should be free from magnesium chloride if thecalcium content of the alloy is to be above 0.3 per cent. In those I Forexample, it will be noted.

instances where an alloy is to be compounded containing less than 0.3per cent of calcium, magnesium chloride may be present in the fluxwithout exerting a deleterious efiect, but in this case it is usuallypreferable to add the calcium last and without too much stirring inorder that the loss of calcium into the flux will be substantiallyprevented.

I claim:

1. A magnesium base alloy containing from 0.5 to 10 per cent of silver,from 0.05 to 1 per cent of calcium, and from 11:0 15 per cent ofcadmium, the balance being magnesium.

2. A magnesium base alloy containing from 2 to 8 per cent'of silver,from 0.1 to 0.5 per cent of calcium, and from 4 to 10 per cent ofcadmium, the balance being magnesium.

3. A magnesium base alloy containing from 3 to 6 per cent of silver,from 0.1 to 0.3 per cent of calcium, and from 6 to 8 per cent ofcadmium, 20

the balance being magnesium.

JOHN C. MCDONALD.

